<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <title>效率测试</title>
</head>

<body>
    

</body>
<script>
    function fn() {
        var d1 = +new Date();
        for (let i = 0; i < 1000; i++) {
            var div = document.createElement('div');
            div.style.width = '100px';
            div.style.height = '2px';
            div.style.border = '1px solid red';
            document.body.appendChild(div);
        }
        var d2 = +new Date();
        console.log(d2 - d1);
    }
    fn();
</script>

</html>